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Our spatial forecasts give a probability that at least one case will be reported in each health zone at various time horizons and are displayed on the interactive map. Select either:
Cases to date: for the number of cases in each health zone during this outbreak
7 day forecast: for the risk of observing cases in each health zone in the next 7 days
14 day forecast: for the risk of observing cases in each health zone in the next 14 days
28 day forecast: for the risk of observing cases in each health zone in the next 28 days
Health zones outlined in red show those where cases have been reported earlier in the outbreak.
We used a poisson model to forecast risk of of cases occuring within 7, 14 and 28 days from the forecast date. The number of cases in a particular health zone at a particular time, \(N_{it}\) are assumed to be poisson distributed with a rate, \(\lambda\) dependent on previous cases in the outbreak. The rate is a linear combination of two components:
the autoregressive component. This accounts for ongoing transmission within a health zone based on cases within that health zone in the past.
The spatial componenet. This accounts for the rate of importation of cases into each health zone based on previous cases in other health zones. This rate is proportional to a gravity kernal, \(\omega_{ij}\), which describes a power law with distance, \(d_{ij}\) weighted by the population of the health zones, \(P_{i}\) and \(P_{j}\).
\[\lambda = \sum_{\tau=t - (D+L)}^{t-L}(\gamma N_{i\tau} + \sum_{j≠i}\alpha \omega _{ij}N_{j\tau})\] \[N_{i,t} \sim ℘(λ_{i,t})\]
\[\omega_{ij}=\frac{P_i P_j}{d_{ij}^k}\]
Parameters in the model (\(\gamma\), \(\alpha\) and \(k\)) were fitted to the previous 60 days of the outbreak using hamiltonian monte carlo via Stan. The joint posterior distribution was then used to project cases into the future using the same model.
The current outbreak of Ebola in the Democratic Republic of the Congo began in Septeber 2018 in the province of North Kivu. The outbreak has since affected a large portion of this province and some parts of the ituri province to the north.